Synthesis method and application of a catalyst for preparing formaldehyde by methanol oxidation

Abstract

The application provides a synthesis method and application of a catalyst for preparing formaldehyde by oxidizing methanol, and belongs to the field of catalyst preparation. The iron-molybdenum catalyst containing an additive is synthesized in a micro-channel reactor, the catalyst has high utilization rate of metal elements, light density, uniform granularity, high catalytic stability, high forming strength and long service life. The catalyst is filled in a fixed bed and used for preparing formaldehyde by oxidizing methanol, so that the polymerization of the reaction is reduced, the selectivity of the catalyst is improved, the loss of active components is reduced, and the service life of the catalyst is prolonged. The synthesis process of the catalyst is simple, the catalyst has small and uniform particle size, no flaky impurity crystals, high utilization rate of metal elements, and plays a positive role in treating wastewater generated in the later catalyst production.

Description

Technical Field

[0001] This invention belongs to the field of catalyst processing technology, and particularly relates to a synthesis method and application of a catalyst for the oxidation of methanol to formaldehyde. Background Technology

[0002] Formaldehyde is an important downstream product of methanol and a raw material for organic chemicals. It is one of the common platform molecules in C1 and low-carbon chemicals. Its derivatives include formaldehyde polymers, trialdehyde resins, 1,4-butanediol, polyvinyl alcohol acetal fibers, diphenylmethane diisocyanate, hexamethylenetetramine, tetramethylolmethane, methyl acetal, acrylic acid and its esters, polyoxymethylene dimethyl ether, and ethylene glycol. There are two commonly used methods for formaldehyde production both domestically and internationally: the silver catalytic method and the iron-molybdenum catalytic method. The former has been gradually replaced by the iron-molybdenum method due to the high cost of catalysts, high catalytic reaction temperature, and low formaldehyde concentration produced.

[0003] Compared to the silver method, the "iron-molybdenum method" has lower operating temperature, lower raw material consumption, greater potential for waste heat utilization, longer single-pass operation cycle, higher product concentration, and lower safety risks. Overall, in large-scale methanol oxidation to formaldehyde production, the "iron-molybdenum method" has better economics and stronger competitiveness than the "silver method".

[0004] Currently, numerous studies worldwide have reported on iron-molybdenum catalysts for the oxidation of methanol to formaldehyde. However, due to the tunable diversity of iron and molybdenum species during the preparation process, especially since molybdenum is an isopolyacid or heteropolyacid source, different acidities during preparation can cause changes in factors such as the degree of molybdate polymerization and species structure, thus affecting the catalyst's structure and performance. For example, the formation of lamellar molybdenum trioxide impurities during preparation directly affects the catalyst's strength, activity, and lifespan. Furthermore, in the "iron-molybdenum catalytic method," carbon monoxide poisoning and elemental loss can also lead to catalyst deactivation and reduce its lifespan. Summary of the Invention

[0005] In view of this, the present invention provides a synthesis method for a catalyst for the oxidation of methanol to prepare formaldehyde. The preparation method of the present invention is simple and feasible, the prepared catalyst has high metal element utilization rate, and the catalyst has light density and uniform particle size, which is beneficial to the stability of catalyst performance; it also has high molding strength, which is beneficial to improving the service life of the catalyst.

[0006] The technical solution of the present invention is as follows: a synthesis method for a catalyst for the preparation of formaldehyde by methanol oxidation, wherein a molybdenum source solution, an iron source and an auxiliary agent are respectively introduced into a microchannel reactor for reaction, and the product is successively filtered, dried and calcined to obtain the catalyst; wherein the auxiliary agent is at least one of cerium salt, zirconium salt, chromium salt, copper salt, nickel salt and silver salt.

[0007] In some specific technical solutions, the atomic ratio of molybdenum to iron in the catalyst is 2.1~2.5:1, and the mass content of the additive, calculated as oxide, is 0.01~1% of the catalyst.

[0008] In some specific technical solutions, the atomic ratio of molybdenum to iron in the catalyst is 2.2~2.4:1, and the mass content of the additive, calculated as oxide, is 0.01~0.5% of the catalyst.

[0009] In some specific technical solutions, the pH value of the molybdenum source solution is 6.0~6.5; and the pH value of the mixed solution of iron source and additives is 1.0~1.08.

[0010] In some specific technical solutions, the reaction temperature in the microchannel reactor is 50~80℃.

[0011] In some specific technical solutions, the auxiliary agent is at least one of cerium nitrate, zirconium nitrate, chromium nitrate, copper nitrate, nickel nitrate, and silver nitrate.

[0012] In some specific technical solutions, the reaction temperature in the microchannel reactor is 60~70℃.

[0013] Some specific technical solutions involve aging the product at 50~80 ℃ for 0~48 h before filtration.

[0014] Some specific technical solutions involve washing the product until the pH of the washing water is greater than 2.5, and then drying it at 70~100 ℃.

[0015] Some specific technical solutions involve the following roasting process: pre-roasting at 250~350 ℃ for 8~20 h, followed by crushing, granulation, and tableting, then roasting at 250~350 ℃ for 8~20 h, and finally roasting at 380~450 ℃ for 2~10 h.

[0016] In some specific technical solutions, drying and calcination are carried out in an air atmosphere with a heating rate of 0.5℃ / min.

[0017] The molybdenum source and iron source are both selected from commonly used raw materials of ferromolybdenum catalysts for the synthesis of formaldehyde by oxidizing methanol.

[0018] Specifically, the molybdenum source is selected from ammonium heptamolybdate and ammonium molybdate, and the iron source is ferric nitrate.

[0019] This invention provides a specific method for synthesizing a catalyst for the oxidation of methanol to formaldehyde, the specific steps of which are as follows:

[0020] (1) Raw material preparation

[0021] Prepare salt solution M by adding ammonium molybdate to water; prepare salt solution F by adding ferric nitrate (nonahydrate) and additives to water.

[0022] (2) Reactions are carried out in microreactors

[0023] F and M are fed into the microchannel reactor in parallel; after exiting the microchannel, the material is aged.

[0024] (3) The aged slurry is filtered, washed, dried, pre-calcined, shaped, and calcined to obtain the catalyst.

[0025] In the above method, during the preparation of the molybdenum source solution, in order to promote the dissolution of the molybdenum source, the temperature of the solvent or the molybdenum source solution can be raised to 40℃~45℃, and ammonia water can be used to adjust the pH value of the molybdenum source solution or the mixed solution of iron source and auxiliary agent.

[0026] In the above method, the product is filtered, washed, dried, pre-calcined, shaped, and calcined; washing is performed until the pH of the washing water is greater than 2.5; drying is carried out at 70~100 ℃; the product is heated at room temperature in an air atmosphere at a rate of 0.5 ℃ / min, calcined at 250~350 ℃ for 8~20 h, and then cooled naturally; after pre-calcination, the product is crushed, granulated, and pressed into tablets; the product is heated at room temperature in an air atmosphere at a rate of 0.5 ℃ / min, calcined at 250~350 ℃ for 8~20 h, and then calcined at 380~450 ℃ for 2~10 h, and then cooled naturally.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention provides a method for synthesizing a catalyst for the methanol oxidation to formaldehyde production. A molybdenum source, an iron source, and an additive are mixed and reacted in a microchannel reactor. This process ensures that the prepared catalyst particles are uniform and free from the formation of flaky molybdenum trioxide, thereby improving catalyst strength, slowing catalyst wear, and increasing catalyst lifespan. Simultaneously, it enhances the utilization rate of iron and molybdenum metals. Furthermore, the addition of the additive improves the selectivity of formaldehyde and the conversion rate of methanol during the methanol oxidation to formaldehyde production process. In summary, the catalyst preparation process provided by this invention is simple and convenient to operate, with high utilization of the metal elements used in the catalyst, reducing the loss of iron and molybdenum during synthesis, reducing the concentration of iron and molybdenum in wastewater, and achieving cost reduction and environmental pollution reduction. Attached Figure Description

[0029] Figure 1 The flowchart below shows the evaluation process for the catalyst synthesized in the examples.

[0030] Figure 2 The image shown is an electron microscope image of the catalyst prepared in Example 1.

[0031] Figure 3 The image shown is an electron microscope image of the catalyst prepared in Example 2.

[0032] Figure 4 Electron micrograph of the catalyst prepared in Example 8.

[0033] Figure 5 Electron micrograph of the catalyst prepared in Comparative Example 1. Detailed Implementation

[0034] The present invention will be further described below with reference to the embodiments.

[0035] The microchannel reactor selected in the specific embodiment of the present invention is model WH-IND MIXER-M4. Example 1

[0036] Preparation of raw materials: Add 85.125 g of ammonium heptamolybdate to 1000 g of deionized water at 40 ℃ to prepare salt solution M, and adjust the pH of the solution to 6.5 with ammonia. Add 85.5 g of raw material (nonahydrate) ferric nitrate and 0.1 g of cesium nitrate to 1000 g of deionized water at 25 ℃ to prepare solution F, and adjust the pH of the solution to 1.01 with ammonia.

[0037] Microreactor reaction: M and F are pumped into the microchannel reactor in parallel flow. The temperature of the water bath in the microreactor is 67 ℃, and the reaction time is 1 h (ensuring that they are added dropwise at the same time). After discharge, the solution is aged at 70 ℃ for 24 h. During the aging process, the pH of the solution is monitored to be around 2.0.

[0038] Post-treatment: The aged slurry was filtered (Mo: 150 ppm; Fe: 10 ppm in the mother liquor), washed until the pH of the washing water was 2.6, and the filtered and washed filter cake was dried at 90℃ for 24 h. The dried filter cake was pre-calcined at room temperature in an air atmosphere with a heating rate of 0.5 ℃ / min, calcined at 300℃ for 14 h, and then allowed to cool naturally. After pre-calcination, the catalyst was crushed, granulated, and pressed into tablets, then demolded. The calcination conditions for the calcined catalyst were a bogie furnace calcination at room temperature in an air atmosphere with a heating rate of 0.5 ℃ / min, held at 300℃ for 14 h, calcined at 420℃ for 8 h, and then allowed to cool naturally. Catalyst BET=5.5 m 2 / g. Example 2

[0039] Preparation of raw materials: Add 85.125 g of ammonium heptamolybdate to 1000 g of deionized water at 45 ℃ to prepare salt solution M, and adjust the pH of the solution to 6.5±0.2 with ammonia. Add 94.02 g of ferric nitrate (nonahydrate) and 0.11 g of zirconium nitrate to 1000 g of deionized water to prepare solution F, and adjust the pH of the solution to 1.05 with ammonia.

[0040] Microreactor reaction: M and F are pumped into the reactor in parallel flow. The water bath temperature of the microreactor is 67℃, and the reaction time is 1 hour (ensuring that they are added dropwise at the same time). After discharge, the material is aged at 70℃ for 25 hours. During the aging process, the pH value of the solution is monitored to be around 2.0.

[0041] Post-treatment: The aged slurry was filtered (Mo: 140 ppm; Fe: 10 ppm in the mother liquor), washed until the pH of the washing water was 2.6, and the filtered filter cake was dried at 90℃ for 24 hours. The dried filter cake was pre-calcined: at room temperature under air atmosphere, the initial heating rate was 0.5℃ / min, calcined at 300℃ for 14 hours, and then allowed to cool naturally. After pre-calcination, the cake was crushed, granulated, and pressed into tablets, then demolded. The catalyst was then calcined in a bogie hearth furnace under air atmosphere: at room temperature, the initial heating rate was 0.5℃ / min, held at 300℃ for 14 hours, calcined at 420℃ for 8 hours, and then allowed to cool naturally. Catalyst BET = 5.7m 2 / g. Example 3

[0042] Preparation of raw materials: Add 85.125 g of ammonium heptamolybdate to 1000 g of deionized water at 40 ℃ to prepare salt solution M, and adjust the pH of the solution to 6.5 ± 0.2 with ammonia. Add 89.92 g of ferric nitrate (nonahydrate) and 0.11 g of copper nitrate to 1000 g of deionized water to prepare solution F, and adjust the pH of the solution to 1.03 with ammonia.

[0043] Microreactor reaction: M and F are pumped into the reactor in parallel flow. The water bath temperature of the microreactor is 67℃, and the reaction time is 1 hour (ensuring that they are added dropwise at the same time). After discharge, the material is aged at 70℃ for 24 hours. During the aging process, the pH value of the solution is monitored to be around 2.0.

[0044] Post-treatment: The aged slurry was filtered (Mo: 150 ppm; Fe: 10 ppm in the mother liquor), washed until the pH of the washing water was 2.6, and the filtered and washed filter cake was dried at 90℃ for 24 hours. The dried filter cake was pre-calcined at room temperature in an air atmosphere with a heating rate of 0.5℃ / min, calcined at 300℃ for 14 hours, and then allowed to cool naturally. After pre-calcination, the cake was crushed, granulated, and pressed into tablets, which were then demolded. The catalyst was then calcined in a bogie hearth furnace in an air atmosphere with a heating rate of 0.5℃ / min, held at 300℃ for 14 hours, calcined at 400℃ for 8 hours, and then allowed to cool naturally. Catalyst BET=5m 2 / g. Example 4

[0045] Preparation of raw materials: Add 85.125 g of ammonium heptamolybdate to 1000 g of deionized water at 43 ℃ to prepare salt solution M, and adjust the pH of the solution to 6.5 ± 0.2 with ammonia. Add 82.74 g of ferric nitrate (nonahydrate) and 0.11 g of nickel nitrate to 1000 g of deionized water to prepare solution F, and adjust the pH of the solution to 1.05 with ammonia.

[0046] Microreactor reaction: M and F are pumped into the reactor in parallel flow. The water bath temperature of the microreactor is 67℃, and the reaction time is 1 hour (ensuring that they are added dropwise at the same time). After discharge, the material is aged at 70℃ for 24 hours. During the aging process, the pH value of the solution is monitored to be around 2.0.

[0047] Post-treatment: The aged slurry was filtered (Mo: 150 ppm; Fe: 10 ppm in the mother liquor), washed until the pH of the washing water was 2.6, and the filtered and washed filter cake was dried at 90℃ for 24 hours. The dried filter cake was pre-calcined at room temperature in an air atmosphere with a heating rate of 0.5℃ / min, calcined at 300℃ for 14 hours, and then allowed to cool naturally. After pre-calcination, the cake was crushed, granulated, and pressed into tablets, which were then demolded. The catalyst was then calcined in a bogie hearth furnace in an air atmosphere with a heating rate of 0.5℃ / min, held at 300℃ for 14 hours, calcined at 400℃ for 8 hours, and then allowed to cool naturally. Catalyst BET=5m 2 / g. Example 5

[0048] Preparation of raw materials: Dissolve 85.125g of ammonium heptamolybdate in 1000g of deionized water at 40℃ to prepare salt solution M, and adjust the pH of the solution to 6.5±0.2 with ammonia. Add 89.92g of ferric nitrate (nonahydrate) and 0.014g of silver nitrate to 1000g of deionized water to prepare solution F, and adjust the pH of the solution to 1.01 with ammonia.

[0049] Microreactor reaction: M and F are pumped into the reactor in parallel flow. The water bath temperature of the microreactor is 67℃, and the reaction time is 1 hour (ensuring that they are added dropwise at the same time). After discharge, the material is aged at 70℃ for 24 hours. During the aging process, the pH value of the solution is monitored to be around 2.0.

[0050] Post-treatment: The aged slurry was filtered (Mo: 150 ppm; Fe: 10 ppm in the mother liquor), washed until the pH of the washing water reached 2.6, and the filtered and washed filter cake was dried at 90℃ for 24 hours. The dried filter cake was pre-calcined at room temperature in an air atmosphere with a heating rate of 0.5℃ / min, calcined at 300℃ for 14 hours, and then allowed to cool naturally. After pre-calcination, the cake was crushed, granulated, and pressed into tablets, which were then demolded. The catalyst was then calcined in a bogie hearth furnace in an air atmosphere with a heating rate of 0.5℃ / min, held at 300℃ for 14 hours, calcined at 400℃ for 8 hours, and then allowed to cool naturally. The catalyst's BET was 5.2 m. 2 / g. Example 6

[0051] Preparation of raw materials: Add 85.125g of ammonium heptamolybdate to 1000g of deionized water at 45℃ to prepare salt solution M, and adjust the pH of the solution to 6.5±0.2 with ammonia. Add 89.92g of ferric nitrate (nonahydrate) and 0.15g of chromium nitrate to 1000g of deionized water to prepare solution F, at 25℃, and adjust the pH of the solution to 1.05 with ammonia.

[0052] Microreactor reaction: M and F are pumped into the reactor in parallel flow. The water bath temperature of the microreactor is 67℃, and the reaction time is 1 hour (ensuring that they are added dropwise at the same time). After discharge, the material is aged at 70℃ for 24 hours. During the aging process, the pH value of the solution is monitored to be around 2.0.

[0053] Post-treatment: The aged slurry was filtered (Mo: 150 ppm; Fe: 10 ppm in the mother liquor), washed with water until the pH of the washing water was 2.6, and the filtered filter cake was dried at 90℃ for 24 hours. The dried filter cake was pre-calcined at room temperature in an air atmosphere with a heating rate of 0.5℃ / min, calcined at 300℃ for 14 hours, and then allowed to cool naturally. After pre-calcination, the cake was crushed, granulated, and pressed into tablets, which were then demolded. The catalyst was then calcined in a bogie hearth furnace in an air atmosphere with a heating rate of 0.5℃ / min, held at 300℃ for 14 hours, calcined at 400℃ for 8 hours, and then allowed to cool naturally. The catalyst's BET was 5.3 m. 2 / g. Example 7

[0054] Raw material preparation: Add 85.125g of ammonium heptamolybdate to 1000g of deionized water at 40℃ to prepare salt solution M, and adjust the pH of the solution to 6.4 with ammonia. Add 85.5g of ferric nitrate (nonahydrate) and 0.62g of cesium nitrate to 1000g of deionized water to prepare salt solution M, and adjust the pH of the solution to 1.05 with ammonia.

[0055] Microreactor reaction: M and F are pumped into the reactor in parallel flow. The water bath temperature of the microreactor is 67℃, and the reaction time is 1 hour (ensuring that they are added dropwise at the same time). After discharge, the material is aged at 70℃ for 24 hours. During the aging process, the pH value of the solution is monitored to be around 2.0.

[0056] Post-treatment: The aged slurry was filtered (Mo: 150 ppm; Fe: 10 ppm in the mother liquor), washed with water until the pH of the washing water was 2.6, and the filtered filter cake was dried at 90℃ for 24 hours. The dried filter cake was pre-calcined at room temperature in an air atmosphere with a heating rate of 0.5℃ / min, calcined at 300℃ for 14 hours, and then allowed to cool naturally. After pre-calcination, the cake was crushed, granulated, and pressed into tablets, which were then demolded. The catalyst was then calcined in a bogie hearth furnace in an air atmosphere with a heating rate of 0.5℃ / min, held at 300℃ for 14 hours, calcined at 420℃ for 8 hours, and then allowed to cool naturally. The catalyst's BET was 5.5m. 2 / g. Example 8

[0057] Preparation of raw materials: Add 85.125 g of ammonium heptamolybdate to 1000 g of deionized water at 40 ℃ to prepare salt solution M, and adjust the pH of the solution to 6.5 with ammonia. Add 85.5 g of raw material (nonahydrate) ferric nitrate and 0.1 g of cesium nitrate to 1000 g of deionized water at 25 ℃ to prepare solution F, and adjust the pH of the solution to 1.01 with ammonia.

[0058] Microreactor reaction: M and F are pumped into the microchannel reactor in parallel flow. The temperature of the water bath in the microreactor is 67 ℃, and the reaction time is 1 h (ensuring that they are added simultaneously). The product is then discharged.

[0059] Post-treatment: The discharged slurry was filtered (Mo: 150 ppm; Fe: 10 ppm in the mother liquor), washed until the pH of the wash water was 2.6, and the filtered filter cake was dried at 90℃ for 24 h. The dried filter cake was pre-calcined at room temperature in an air atmosphere with a heating rate of 0.5℃ / min, calcined at 300℃ for 14 h, and then allowed to cool naturally. After pre-calcination, the catalyst was crushed, granulated, and pressed into tablets, then demolded. The calcination conditions for the calcined catalyst were a bogie hearth furnace, with a heating rate of 0.5℃ / min in an air atmosphere, held at 300℃ for 14 h, calcined at 420℃ for 5 h, and then allowed to cool naturally. Catalyst BET = 5.5 m 2 / g.

[0060] Comparative Example 1

[0061] Preparation of raw materials: Add 85.125 g of ammonium heptamolybdate to 1000 g of deionized water at 40 ℃ to prepare salt solution M, and adjust the pH of the solution to 6.5 with ammonia. Add 85.5 g of raw material (nonahydrate) ferric nitrate and 0.1 g of cesium nitrate to 1000 g of deionized water at 25 ℃ to prepare solution F, and adjust the pH of the solution to 1.01 with ammonia.

[0062] Heating reaction: M and F were pumped into a four-necked flask reactor in parallel flow. The reactor water bath temperature was 67 ℃, and the reaction time was 1 h (ensuring that they were added dropwise at the same time). Aging was carried out at 70 ℃ for 24 h. During the aging process, the pH of the solution was monitored to be around 2.0.

[0063] Post-treatment: The aged slurry was filtered (Mo: 150 ppm; Fe: 10 ppm in the mother liquor), washed until the pH of the washing water was 2.6, and the filtered and washed filter cake was dried at 90℃ for 24 h. The dried filter cake was pre-calcined at room temperature in an air atmosphere with a heating rate of 0.5 ℃ / min, calcined at 300℃ for 14 h, and then allowed to cool naturally. After pre-calcination, the catalyst was crushed, granulated, and pressed into tablets, then demolded. The calcination conditions for the calcined catalyst were a bogie furnace calcination at room temperature in an air atmosphere with a heating rate of 0.5 ℃ / min, held at 300℃ for 14 h, calcined at 420℃ for 8 h, and then allowed to cool naturally. Catalyst BET=5.5 m 2 / g.

[0064] Test case

[0065] The microstructure of the samples was observed using a HITACHI SU5000 scanning electron microscope from HITACHI Corporation of Japan. For example... Figure 2-4 As shown, the catalyst prepared by the method of the present invention has a uniform particle size and no plate-like molybdenum oxide is generated.

[0066] Figure 1 The flowchart for catalyst evaluation is shown. Catalyst activity testing was conducted using a stainless steel fixed-bed tubular reactor with a tube diameter of Φ25*2mm and a reactor length of 160 cm. The outer diameter of the temperature measuring sleeve was 4.5 mm. The catalyst loading scheme was consistent with that of the industrial plant. The loading scheme from top to bottom was: 30cm inert rings, 33cm 45 vol% diluted catalyst 1, 17cm 65 vol% diluted catalyst 2, 53cm pure catalyst, and a bottom 7cm inert ring. The catalyst was diluted to the required concentration using ceramic rings.

[0067] Evaluation conditions: System pressure was atmospheric pressure, reaction inlet temperature was 200℃, initial heat transfer oil temperature was 260-270℃, and catalyst performance indicators were: methanol inlet concentration 10% and volume hourly space velocity 8500-9000 h⁻¹. -1Methanol consumption is <0.428 tons (based on 37% formaldehyde aqueous solution per ton), and the characteristic formaldehyde yield under high air velocity process conditions (full load) is ≥18 tons / kg.cat. Specific feed rates are as follows: methanol feed rate approximately 6.2 g / min, air feed rate approximately 22.5 L / min, and nitrogen feed rate approximately 15.5 L / min.

[0068] The catalytic performance of the catalysts prepared in the specific embodiments for the oxidation of methanol to formaldehyde is shown in Table 1. As can be seen from Table 1, the catalysts prepared in this invention exhibit high selectivity for formaldehyde, while the conversion rates of methanol are all greater than 97%. Even after 4000 hours of operation, the catalysts maintain high selectivity and conversion rates.

[0069] Table 1 Performance indicators of the catalysts prepared in the examples for methanol oxidation

[0070]

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for synthesizing a catalyst for the oxidation of methanol to formaldehyde, characterized in that, The molybdenum source solution, the iron source and the additive were respectively passed into a microchannel reactor for reaction, and the product was successively filtered, dried and calcined to obtain the catalyst. The additive is at least one of cerium salt, zirconium salt, chromium salt, copper salt, nickel salt, and silver salt; The pH value of the molybdenum source solution is 6.0~6.5; the pH value of the mixed solution of iron source and additives is 1.0~1.

08. The reaction temperature in the microchannel reactor is 50~80℃.

2. The synthesis method for the catalyst for the methanol oxidation to formaldehyde according to claim 1, characterized in that, The atomic ratio of molybdenum to iron in the catalyst is 2.1 to 2.5:1, and the auxiliary agent, calculated as oxide, accounts for 0.01 to 1% of the catalyst by mass.

3. The synthesis method for the catalyst for the methanol oxidation to formaldehyde according to claim 2, characterized in that, The atomic ratio of molybdenum to iron in the catalyst is 2.2~2.4:1, and the auxiliary agent, calculated as oxide, accounts for 0.01~0.5% of the catalyst by mass.

4. The method for synthesizing a catalyst for the oxidation of methanol to formaldehyde according to any one of claims 1-3, characterized in that, The auxiliary agent is at least one of cerium nitrate, zirconium nitrate, chromium nitrate, copper nitrate, nickel nitrate, and silver nitrate.

5. The method for synthesizing a catalyst for the oxidation of methanol to formaldehyde according to any one of claims 1-3, characterized in that, The reaction temperature in the microchannel reactor is 60~70℃.

6. The method for synthesizing a catalyst for the oxidation of methanol to formaldehyde according to any one of claims 1-3, characterized in that, The product was aged at 50-80 ℃ for 0-24 h before filtration.

7. The method for synthesizing a catalyst for the oxidation of methanol to formaldehyde according to any one of claims 1-3, characterized in that, The product is washed until the pH of the wash water is greater than 2.5; then dried at 70-100℃. The roasting process is as follows: pre-roasting at 250~350℃ for 8~20h, crushing, granulating and pressing into tablets, roasting at 250~350℃ for 8~20h, and then roasting at 380~450℃ for 2~10h.

8. The method for synthesizing a catalyst for the oxidation of methanol to formaldehyde according to claim 7, characterized in that, Both drying and calcination were carried out in air at a heating rate of 0.5℃ / min.

9. A catalyst synthesized by the synthetic method according to any one of claims 1-3.

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